a) Field of the Invention
The invention is directed to a device for transporting wafer magazines by means of an elevator between an upper removal position in which the magazine is removed from a magazine container and a lower depositing position from which transfer is carried out to at least one processing location.
b) Description of the Related Art
Systems which have become known as SMIF (Standard Mechanical Interface) systems and are favored in the fabrication of semiconductor chips contain a so-called SMIF box as a magazine container with a relatively small enclosed volume in which wafer magazines can be stored and transported. The box can be placed on an opening mechanism in an enclosure surrounding one or more work stations so as to protect them from dust. The box and opening mechanism have closing elements which are adapted to one another and can be opened simultaneously one above the other so that dust particles which have settled on the outside of the closing elements can be trapped between them when the wafer magazine is lowered into the enclosure together with the two closing elements. The box itself surrounds the opening made in the enclosure.
After the magazine has been deposited, it is generally necessary to effect a transfer within the enclosure. Various technical solutions are known to carry out such transfer.
For example, in EP 209 660 a cassette is transported from a SMIF elevator to a device elevator by an automated cassette manipulator in that a swiveling movement is effected during the vertical movement for lifting or lowering the cassette. The use of rotating members is intended to reduce the degree of particle generation compared with linearly moving members.
Similar solutions are also described in EP 238 541, in which the magazine is transferred along given movement curves by motor-operated lever arms which are moved in the Z-direction by means of a separate lift.
The laminar flow of air required to maintain the clean room is critically disturbed or prevented due to the mechanical construction in the known solutions, in particular due to the fact that the working range of the transfer device which is constructed as a lever arm occurs laterally to the magazine and as a result of the closed construction. Coupling the transfer movement with the Z-movement unnecessarily prolongs transport times and increases particle generation.
Particularly when retrofitting machinery for semiconductor processing, it is difficult in the known technical solutions to supplement already existing clean rooms with the SMIF system so as to allow wafer magazines to be introduced into the primary machines under SMIF conditions and unpacked and transported in the machines under clean room conditions.